1. Field of the Invention
The invention relates to a hydrocyclone apparatus for separating a mixed phase input stream into its constituent parts, such as performing a solid/liquid/gas separation or separation of two immiscible liquids. Separation is effected by differentiation of the phases based on their specific gravity, as a result of centifugal force imparted to the stream by virtue of the cyclonic action.
The claimed system comprises a hydrocyclone specially designed to process this three phase system, characterized by a unique structure comprising a helical cyclonic path situated in a discrete annular conical space between two nesting conical chambers.
2. Description of the Prior Art
In general, a hydrocyclone consists of an inverted conical chamber. A mixed stream, e.g. consisting of liquid/solid or high density liquid/low density liquid, is input into the chamber tangentially, at very high velocity, towards the top of the chamber, i.e. the base of the cone. The high angular accelaration of the stream imparts a centrifugal force which acts upon the different densities of the stream components. The heavier component is thrust against the cone wall, spiraling downward in a helical manner for collection at an outlet port below, while the lighter fraction tends radially inwardly, and upwardly by virtue of the pressure drop created by the cylcone.
Attempts have been made to increase the separation effectiveness by providing a further chamber outside of the principal chamber. Thus, U.S. Pat. Nos. 5,300,222 and 5,407,584, related patents both issued to Broussard, teach an apparatus for separating oil, water, sand and vapor. A cyclone is situated within a large separation tank. The cyclone comprises an outer cylindrical shell and inner coaxial cylindrical shell, and an annular space therebetween. The mixture enters through a circular inlet pipe in a tangential orientation into the annular space. The heavier water and sand are forced to the outside of the space, against the inner wall of outer shell, as the mixture spirals down the annular space. The inner shell ends at a point where the outer shell forms a conically shaped shell. The conical shell portion is hollow, and does not have an annular or conical space defined.
Others have attempted to impart a porosity to the wall of the principal conical chamber, in conjunction with a further chamber situated outside the principal chamber. U.S. Pat. No. 4,048,067 to Cheng teaches a hydrocyclone having a conical annular space. The inner conical wall is perforated and has a porous lining, which is impervious to solids. A solid/liquid mixture enters the inner conical chamber, and the solids are retained in the porous lining while the heavier liquid passes through into the conical annular space, and through an outlet. The retained solids are washed away through a further outlet at the bottom of the inner conical chamber. Lighter liquids are taken up through an outlet in a usual manner and recycled through the system. However, the conical annular space is merely a collecting area for liquids passing through the porous wall. This apparatus relies on the centrifugal force created to enhance the separation of the solids by way of a filtering means. However, this is in some regard working against the cyclonic effect by relying on the lighter liquids to pass out to the outer chamber, while trapping the heavier solids inside the main conical chamber. Furthermore, the filtering means will quickly become clogged with entrained solids, reducing effectiveness, and requiring periodic cleaning.
U.S. Pat. No. 4,097,375 to Molitor teaches a hydrocyclone for separating dissolved salt from a water stream. The lighter liquids tend toward the center of the central cone, and flow out through the top through an upper outlet, with the heavier liquids tending toward the wall of the cone, and eventually flowing out the bottom through a bottom outlet. The liquid containing salt is heaviest, and is circulated by centrifugal force against a wall portion, comprising a porous medium which separates out the salt fraction. The clean water then flows into the annular frustoconical chamber adjacent the wall portion. The action and structure of this device is similar to the Cheng device discussed above, in that in both cases, the porous shells act as filters, retaining the heavier solids within the inner cyclone space, while allowing the clean liquid to pass through to the outer receiving chamber. The same drawbacks apply here.